Any chance you could take a quick cell phone video of him using his current trackpad so we can see what his motion is like? For the sake of finding alternatives, I think this would help more than anything.

Also, IIRC you can get a program on a modded PSP (maybe even unmodded) that will let you use the PSP joystick as a mouse. I'm not sure how many other devices use that joystick as I'm pretty sure it was developed specifically for the PSP, but I may be wrong.

edit: would this work?